Oligonucleotides polymer-supported reagents

One widely used method involving protected compounds is solid-phase syn-thesis (polymer-supported reagents). This method has the advantage of simple workup by filtration and automated syntheses, especially of polypeptides, oligonucleotides, and oligosaccharides. 

Oligonucleotide Synthesis with Polymer-Supported Reagents... 

Figure 19.17 Polymer-supported reagents used for oligonucleotide synthesis.

The first nucleotide is attached to the functional soluble polymer via the phosphate group. After cleavage of the protecting group, reagents and other low-molecular compounds are separated by membrane filtration. Then, the product can be controlled analytically and the next nucleotide units are coupled repeatedly in the same cycle until the desired length of the oligonucleotide is attained. FinaUy, the product is cleaved chemically or enzymatically from the polymer support... 

More recently, automated gene synthesizers have been developed that operate on principles similar to the Merrifield solid-phase technique for peptides. A protected nucleotide is covalently bonded to a polymer. Other protected nucleotides are then added sequentially to the chain, using a coupling reagent. Eventually, the protecting groups are removed, and the synthetic oligonucleotide is then detached from the solid support. 

The solid phase synthesis of oligonucleotides has not reached the level of sophistication as that for peptides. The design of an appropriate solid support has been difficult with such problems as undesirable polymer characteristics and irreversible adsorption of reagents onto the support. Only recently have appropriate polymer matrices (e.g., HPLC silica) been described that appear to have potential for the synthesis of nucleotide polymers. In fact, a major impetus for the development of solid phase methodology for the synthesis of polydeoxyribonucleotide (DNA) sequences has been the industrial application of the so-called biotechnology or recombinant DNA technology. 

Many advantages arise from this S5mthetic process. First of all, the oligonucleotide synthesis is carried out in homogeneous media since the chain to be synthesised is linked to a soluble supporting polymer. The polymer-bound product is recovered from the reaction mixture by a simple precipitation that allows rapid and easy elimination of excess reagents and... 

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